I'm running an 70w aquamedic ocean light on my 5g nano. it's complete, with an attractive pendant, for about $240. the dr. lamp DIY kit is nicely priced, but after the cost of the DIY pendant, and the time it takes to put it together, it's not much cheaper. the ocean light also comes with 10k and 20k options (i'm using the 20k
)
the AM is also well-designed. it comes with mounting hardware, the ballast has a built-in fan, and the spring loaded sockets are light years better than the ones in the PFO pendant (i've broken a bulb or two with the PFO sockets)
djconn: 70w is plenty bright for my 5g, but i would go with a 150w for a 20H.